This invention relates to personal computers used as local area network (LAN) servers, and more particularly to unattended activation and operation of such personal computers through cooperation of power supplies for supplying electrical power to electrically operated components which manipulate or store digital data with options added to the personal computer in adapting the personal computer to the LAN server function.
Personal computer systems in general and IBM personal computers in particular have attained widespread use for providing computing capability to many segments of today's modern society. Personal computer systems can usually be defined as a desk top, floor standing, or portable microcomputer that consists of a system unit having a single system processor and associated volatile and non-volatile memory, a display monitor, a keyboard, one or more diskette drives, a fixed disk storage, and an optional printer. One of the distinguishing characteristics of these systems is the use of a motherboard or system planar to electrically connect these components together. These systems are designed primarily to give independent computing capability to a single user and are inexpensively priced for purchase by individuals or small businesses. Examples of such personal computer systems are IBM's PERSONAL COMPUTER AT and IBM's PERSONAL SYSTEM/2 Models 25, 30, L40SX, 50, 55, 60, 65, 70, 80, 90 and 95.
Persons familiar with the operation and use of these systems will also be familiar with their use in what are known as local area networks, in which a number of personal computers are connected together for sharing of files and other resources. Certain forms of such networks are known as "client-server" computing environments, in that one or more particularly powerful systems ("servers"), potentially having greatly enlarged file storage capability, are connected with less powerful systems ("clients", sometimes known as LAN stations).
These systems can be classified into two general families. The first family, usually referred to as Family I Models, use a bus architecture exemplified by the IBM PERSONAL COMPUTER AT and other "IBM compatible" machines. The second family, referred to as Family II Models, use IBM's MICRO CHANNEL bus architecture exemplified by IBM's PERSONAL SYSTEM/2 Models 50 through 95. The Family I models typically have used the popular INTEL 8088 or 8086 microprocessor as the system processor. These processors have the ability to address one megabyte of memory. The Family II models typically use the high speed INTEL 80286, 80386, and 80486 microprocessors which can operate in a real mode to emulate the slower speed INTEL 8086 microprocessor or a protected mode which extends the addressing range from 1 megabyte to 4 Gigabytes for some models. In essence, the real mode feature of the 80286, 80386, and 80486 processors provide hardware compatibility with software written for the 8086 and 8088 microprocessors.
Electrical power for energizing the components of such personal computers is conventionally supplied by power supplies which use control logic, switching transistors, power transformers, rectifiers and filters to convert electrical power from an available line voltage and current, such as the 110 volt 60 hertz current supplied in the United States, to the direct voltages and currents required for operation of the personal computer. It has been conventional to control operation of such power supplies by switching the supply voltage to the power supply. In the example given, such switching is accomplished by turning on and off the 110 volt 60 hertz mains supply current.
It has been proposed heretofore, as in Summerlin U.S. Pat. No. 4,723,269, to use a lower level voltage to control the operation of a personal computer power supply. In the Summerlin disclosure, to which the interested reader is referred, a telephone ring detector acts through optically coupled semiconductor devices to control passage of the relatively high voltage supply current. However, such circuitry continues to require manual control over computer power to be exercised by manipulation of a relatively high voltage switch.
A co-pending application owned in common with the present subject invention (Ser. No. 536,751 filed 14 Jun. 1990 and now issued as U.S. Pat. No. 5,008,829) discloses and protects an arrangement in which a user of a personal computer is protected against unnecessary exposure to the relatively high voltage of sources of supply to the personal computer by using logic level voltage, low current electrical signals to enable control over the operation of a personal computer. As recognized there, such use of logic level signals opens the possibility of establishing control over the supply of electrical power to the operating components of a computer in a manner consistent with the manual control used by an operator.
This latter possibility becomes of importance in a client-server computing environment in that resources available only from or through the server will become unavailable to a client when the server is dormant, deactivated or powered-down. As one particular example, an operator seeking to use a particular network outside normal network availability hours would be restricted to resources (programs, files, printers/plotters, etc.) available solely at the individual workstation or client were the network server turned off as is often done for security reasons or to reduce running time and consequent need for service. While a server could conceivably be located and turned on, such systems are often located in places which are either inaccessible or unknown to an individual operator.